Iodine-131 Levels Still Below Levels of Concern

EPA and USDA are monitoring food, rain, and potable water for levels of radioactivity that may have drifted to the United States from Japan.

Mar 31, 2011

On April 4, the U.S. Environmental Protection Agency updated its report on monitoring for radioactive material.

The latest RadNet results include the first results for drinking water: Samples from two locations, Boise, Idaho and Richland, Wash., showed trace amounts of Iodine-131 – about 0.2 picocuries per liter in each case. According to EPA, an infant would have to drink almost 7,000 liters of this water to receive a radiation dose equivalent to a day’s worth of the natural background radiation exposure people experience continuously from natural sources of radioactivity in our environment.

Earlier precipitation samples collected by EPA have shown trace amounts of radioactivity, so the agency has expected to find results such as these in some drinking water samples. Similar findings are to be expected in the coming weeks.

Results of EPA’s precipitation sampling and air filter analyses continue to detect very low levels of radioactive material consistent with estimated releases from the damaged nuclear reactors. These detections were expected and the levels detected are far below levels of public-health concern.

EPA conducts radiological monitoring of milk under its RADNET program, while the U.S. Food and Drug Administration (FDA) has jurisdiction over the safety, labeling, and identity of milk and milk products in interstate commerce. States have jurisdiction over those facilities located within their territory.

Results from a screening sample taken March 25 from Spokane, Wash. detected 0.8 pCi/L of iodine-131, which is more than 5,000 times lower than FDA's Derived Intervention Level. These types of findings are to be expected in the coming days and are far below levels of public health concern, including for infants and children. Iodine-131 has a half-life of approximately eight days, and the level detected in milk and milk products is therefore expected to drop relatively quickly.

“Radiation is all around us in our daily lives, and these findings are a minuscule amount compared to what people experience every day. For example, a person would be exposed to low levels of radiation on a round-trip cross country flight, watching television, and even from construction materials,” said Patricia Hansen, an FDA senior scientist.

EPA’s recommendation to state and local governments is to continue to coordinate closely with EPA, FDA, and the Centers for Disease Control. The environmental agency will continue to communicate nationwide sampling results as they come in.